‘Ōpe‘ape‘a Fanihi Pe‘a vao
Purpose. To provide an introduction to the habitat requirements of bats in Hawai‘i, American Samoa, Guam, and the Commonwealth of the Northern Mariana Islands (CNMI) and general guidance on conservation practices to enhance and manage bat habitats.

INTRODUCTIONThe Hawaiian hoary bat or ‘ōpe‘ape‘a is a medium-sized member of the vesper bat family (Vespertillionidae) which consists of nocturnal, mostly insect-eating bats. It is an endemic subspecies of the North American hoary bat, a solitary tree-roosting species (does not use bat boxes). ‘Ōpe‘ape‘a has frosted brown and gray fur which gives it a hoary appearance. Fur color, frosted or reddish, may be related to location or age. The best time to observe Hawaii’s only native land mammal is at sunset when it comes out to feed. It’s a major predator of night-flying insects such as moths, beetles, and termites. Insectivorous bats play an important role in regulating insect populations of natural and agricultural ecosystems.
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TATUS & DISTRIBUTIONAlthough the number of bats is unknown, resident populations occur on Kaua‘i, Maui, and Hawai‘i and possibly other main islands, with the largest numbers on Kaua‘i and Hawai‘i. Bats occur at all elevations, with the majority of sightings below 7500 ft (2286 m) on Hawai‘i and in lowlands on Kaua‘i. Local occurrence is influenced by insect prey abundance (1). It is a Federal and State endangered subspecies, but many have questioned whether the subspecies is truly endangered with so little known about its status. In 2002, the Hawaiian Hoary Bat Research Cooperative was formed to overcome the challenges of recovering Hawaii’s elusive ‘ōpe‘ape‘a. The cooperative includes over 25 entities representing wildlife conservationists, foresters, agriculturalists, land managers, and researchers working toward sustainable conservation and development.

Photo Honolulu Zoo

REPRODUCTIVE CYCLE ‘Ōpe‘ape‘a appear to make altitudinal migrations between lowland breeding and highland wintering grounds, at least in windward Hawai‘i, spending about May-November in lowlands and January-April in highlands (>5250 ft [1600 m]) (2,3). Although a fall mating period has been suggested (4), the mating period is unknown. Pregnant females have been observed April to August. A 2-3 month gestation (pregnancy) is followed by about a 2-3 month nursing period (5). Females are believed to give birth to twins between May and August and rear pups between May and September. Pups fledge (take first flights) from about July-September, which is a critical time in the reproductive cycle. Although unknown for the Hawaiian subspecies, hoary bat pups in Canada fledge within 4-5 weeks and are weaned at about 7 weeks of age (6).

Water areas. Reservoirs, wetlands, river corridors, and coastal waters for foraging

Food. ‘Ōpe‘ape‘a forage on moths, beetles, termites, leafhoppers, flies, bugs, and other night-flying insects (7). Prey is located using an advanced technique known as echolocation (bats detect size, distance, and shape of prey by emitting and interpreting sound pulses that bounce off objects). In open habitats, medium-sized moths (0.6-0.8 inches [16-20 mm] long) are preferred over large moths (>0.8 inches [20 mm]) and small moths and flies (<0.4 [10 mm]) (8). In forested habitats, bats feed on a variety of small insects (9).

over (roosting). Vegetation cover and structure appear to be more important than tree species, as bats readily use both native and nonnative trees such as eucalyptus, mango, lychee, avocado, albizia, ‘ōhi‘a, and pandanus (12). On Hawai‘i, roosts are located in dense canopy foliage (or subcanopy when canopy is sparse) with open access for launching into flight. Bats generally roost below 15 ft (5 m) in macadamia and Cook pine and above 15 ft (5 m) in eucalyptus (13). There are a few records of bats occurring in lava tubes and other cavities (14,15).
Water. Foods presumably meet water requirements. ‘Ōpe‘ape‘a are not known to drink from water bodies, but are regularly observed foraging over streams, reservoirs, wetlands, stream mouths and out to about 330 ft (100 m) offshore (10). Bats may be attracted to insects of lush riparian vegetation or insects emerging from water, as many flying insects have aquatic larval stages (11).
Interspersion of habitat components. Suitable foraging and roosting habitat near one another is preferable. Although the optimal interspersion (mix of habitat types) is unknown, varied habitat structure near riparian corridors or other insect-rich habitats appears beneficial.
Minimum habitat area. ‘Ōpe‘ape‘a are capable of both high altitude and interisland flight. They require large areas that may encompass multiple landowners. For example, home range (area a bat normally uses for foraging and roosting) for males on a macadamia nut farm averages 124 ac (50 ha), but bats can also commute >7 miles (11 km) from roosts to foraging areas. Home range size varies with habitat type and territories may overlap (5).

Population estimate: 400 - 500 (Aguiguan, CNMI); extirpated (Guam); possibly extirpated (American Samoa)
NTRODUCTIONThe Pacific sheath-tailed bat is a member of the sheath-tailed, sac-winged, and ghost bat family (Emballonuridae), which consists of mainly nocturnal, colonial, cavity-dwelling, insect-eaters. Its name comes from the sheath (little tube) around the tail formed by the uropatagium (skin connecting the tail and hind legs). The sheath allows the bat to adjust the length of its uropagatium in flight and skillfully maneuver the forest understory. The Pacific sheath-tailed bat is a small bat, often mistaken for a swiftlet with which it commonly roosts in caves. Little is known about this rapidly declining species.
STATUS & DISTRIBUTIONPacific sheath-tailed bats occur in the islands of the Marianas, the Carolines, Vanuatu, Fiji, Tonga, and Samoa (4 subspecies). They are common in Palau and Pohnpei in the Carolines, but have greatly declined or disappeared in many other parts of their range in recent decades. One subspecies is known only from the Mariana Islands. The only population of this subspecies contains about 400-500 bats on Aguiguan in the CNMI (16). Bats are now extirpated (locally extinct) on Guam and possibly American Samoa (17-19). They are protected locally in Guam, the CNMI, and American Samoa and are a candidate for Federal listing under the Endangered Species Act.
REPRODUCTIVE CYCLE Almost nothing is known about their breeding biology. A pregnant female with one embryo was collected on Aguiguan in the month of June (17).

HABITAT REQUIREMENTSAlthough information is lacking on habitat requirements, research on the Aguiguan population and general observations from other islands shed light. Pacific sheath-tailed bats generally roost in caves, but large tree hollows are also occupied in Pohnpei. Detailed studies on their echolocation sounds at night show that on Aguiguan they feed mainly in native limestone forest (16). General observations elsewhere suggest that they can also use other native, nonnative, agricultural, and developed landscapes. Habitat examples:

Aguiguan is a 1779-acre (720 ha) limestone island located 5.6 miles (9 km) southwest of the Island of Tinian, CNMI. Here, Pacific sheath-tailed bat habitats include caves along sea cliffs and native forest (Photos P.M. Gorresen, USGS).Food. Pacific sheath-tailed bats forage on small night-flying insects. Prey is located by echolocation (bats detect size, distance, and shape of prey by emitting and interpreting sound pulses that bounce off objects).

Cover (foraging). Bats forage in native and nonnative forested landscapes. On Aguiguan, bats emerge from their caves around the time of sunset to begin foraging. Bats feed on insects in the understory down to <3 ft (1 m) above ground, but also in and above the upper forest canopy and around tall ironwood trees (16,20). On Pohnpei, bats were observed during the day in dense native forest, presumably foraging (21).

USGS research biologists and associates collect data to assess the status of Pacific sheath-tailed bats on Aguiguan, the site of the last known population in the Mariana Islands (Photo E. Valdez, USGS).

Descriptions of threats to Hawaiian hoary bats and Pacific sheath-tailed bats are mostly speculative. Thus, for Hawaiian hoary bats we address potential threats to help prevent these factors from becoming a problem in the future. For Pacific sheath-tailed bats we address suspected threats because populations are disappearing before threats can be identified.

Roost disturbance. Roost disturbance is a common threat to bats worldwide. For Hawaiian hoary bats, this may include: (a) clearing trees that bats roost in, (b) loud unpredictable activities such as building a structure near a bat roosting site, or (c) other human activities that alter normal feeding and breeding patterns or cause direct mortality, which would be violations of Federal and State endangered species laws. Roost disturbance when juvenile hoary bats are fledging (Jul-Sep) has the highest potential for negative impacts (11). Hawaiian hoary bats don’t seem to have high roost site fidelity (may return to the same area but not necessarily the same tree), use roosts seasonally, and are adaptive to human-modified landscapes (5). Pacific sheath-tailed bats readily flush from caves during the day when disturbed. On Aguiguan, some remaining colonies are found in large cliff-side caves inaccessible to humans and feral ungulates (20), suggesting that these bats are sensitive to noise caused during cave intrusions.
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